updated for version 7.3.1303

Problem:    Undo is synced whenever CTRL-R = is called, breaking some plugins.
Solution:   Only break undo when calling setline() or append().

src/globals.h

@@ -916,6 +916,10 @@ EXTERN int no_zero_mapping INIT(= 0);	/* mapping zero not allowed */
 EXTERN int allow_keys INIT(= FALSE);	/* allow key codes when no_mapping
 					 * is set */
 EXTERN int no_u_sync INIT(= 0);		/* Don't call u_sync() */
+#ifdef FEAT_EVAL
+EXTERN int u_sync_once INIT(= 0);	/* Call u_sync() once when evaluating
+					   an expression. */
+#endif
 
 EXTERN int restart_edit INIT(= 0);	/* call edit when next cmd finished */
 EXTERN int arrow_used;			/* Normally FALSE, set to TRUE after